Büyüksaraç, Aydin; Senkaya, Mustafa; Alkan, Hamdi; Bektas, Ozcan; Öztürk, Serkan; Pirti, Atinc; Yücel, Mehmet Ali

The Simav Fault Zone (SFZ) in Western Anatolia remains one of the most active tectonic regions in Turkey, and the 2025 S & imath;nd & imath;rg & imath; earthquake swarm has renewed concern regarding evolving seismic hazard. This study analyzes the swarm on the S & imath;nd & imath;rg & imath; Segment using Coulomb stress modelling, spatial distributions of b- and p-value, gravity and magnetic anomalies, geothermal data, and GNSS observations. Coulomb stress calculations show that the M-W = 6.1 and M-W = 6.0 mainshocks produced stress increases of similar to 0.1 bar that effectively loaded adjacent segments of the SFZ, D & uuml;vertepe Fault Zone (DFZ), and Gelenbe Fault Zone (GFZ), guiding the east-southeast and northward migration of aftershocks. Spatial statistics indicate a b-value ranging from 0.6 to 1.3 and a p-value between 0.3 and 1.0. The lower b-values (< 1.0) and p-values (< 0.5) mark high-stress regions near the mainshock, and higher values characterize more stable zones. Gravity anomalies delineate a dense volcanic-ophiolitic body in the southwest and a caldera-like depression south of the SFZ, while magnetic anomalies highlight the structural continuation and interaction of the SFZ with the GFZ. GNSS stations recorded centimetre-to millimetre-scale motions: BAL1 moved similar to 1.34 cm horizontally with minor uplift, DEI1 experienced similar to 1.12 cm displacement with small vertical fluctuations, and KIKA shifted similar to 0.85 cm southwestward with largely stable elevation. Together, these results show that the 2025 swarm was controlled by stress transfer within a mechanically heterogeneous tectonomagmatic system. The identified stress-enhanced corridors along the SFZ and DFZ may act as future nucleation zones, emphasizing the need for sustained monitoring of this evolving fault network.